Find integer W. (1) W is a prime solution of (|W|)!=|W| (2)

Agreed - I drew the wrong inference

Hi, I was going thru the old question that were shared... can some one explain prime solution?...thanks in advance

Not a GMAT wording.

"W is a prime solution" simply means that \(w\) is a prime number.

So basically the question is:

If w is a prime number, then what is the value of w?

(1) \((|W|)!=|W|\) --> solutions are: -1, 1, -2 and 2. Only one of these values is prime: 2. Hence \(w=2\). Sufficient.

(2) \(W!-|W|=0\) --> solutions are: 1 and 2. Only one of these values is prime: 2. Hence \(w=2\). Sufficient.

Answer: D.

So I guess prime numbers can't be negative no?

Cheers
J

Only positive numbers can be primes. So, the smallest prime number is 2.

How is 1 a solution.. 1! Is 0 which is not equal to absolute value of 1. So IMO, there are only 2 solutions. 2 and -2. And one prime number

_____________
1! is NOT 0. 1! = 1.

E is clearly wrong
(1) gives the solution set as {–2, –1, 1, 2}; 2 is the only prime solution
(2) gives the solution set as {1, 2}; 2 is the only prime solution

W=2
correct answer is D.

Oops !! Sorry ... My bad.. 0! Is 1 , right ? Got confused !!

Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

Find integer W.

(1) W is a prime solution of (|W|)!=|W|
(2) W is a prime solution of W!–|W|=0


In the original condition, there is 1 variable(w), which should match with the number of equation. So you need 1 equation. For 1) 1 equation, for 2) 1 equation, which is likely to make D the answer.
For 1), w=2, which is unique and sufficient
For 2), w=2, which is unique and sufficient.
Therefore, the answer is D.


l For cases where we need 1 more equation, such as original conditions with “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 59 % chance that D is the answer, while A or B has 38% chance and C or E has 3% chance. Since D is most likely to be the answer using 1) and 2) separately according to DS definition. Obviously there may be cases where the answer is A, B, C or E.

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.